Russia's ongoing dismemberment of Ukraine and the Islamic State's erasing of Middle Eastern borders have distracted attention from the harassment of U.S. Navy aircraft by Chinese fighter jets over the South China Sea. Beijing calls this sea, and the Yellow and East China seas, the "near seas," meaning China's seas. The episodes involving aircraft are relevant to one of Adm. Jonathan Greenert's multiplying preoccupations  CUES, meaning Code for Unplanned Encounters at Sea.

This is designed to prevent incendiary accidents, a topic of special interest during this month's centennial commemorations of the beginning of a war that, ignited by miscalculations, ruined the 20th century. Greenert, chief of naval operations, has carrier-based aircraft flying from the Persian Gulf to targets in Iraq. He is, however, always thinking about the far side of the largest ocean.

One hundred years ago, the principal challenge of world diplomacy, which failed spectacularly, was to peacefully integrate a rising, restless power  Germany  into the international system.

Today the Chinese have one primitive aircraft carrier built from a hull bought from Ukraine. Greenert says China is about 10 years away from having a seriously large and capable carrier with excellent aircraft. By which time, optimists hope, China will accept the need for orderliness on the seas over which pass 90 percent of the world's trade (by volume) and beneath which, through cables, pass 95 percent of international phone and Internet traffic.

Greenert's Navy, which has fewer (290) but much more capable ships than the Navy had during the Reagan buildup (594), can still move nimbly to put anti-missile ships near North Korea or F/A-18s over the Islamic State. But cascading dangers are compelling Americans to think afresh about something they prefer not to think about at all  foreign policy.

What they decide that they want will define the kind of nation they want the United States to be. This abstract question entails a concrete one: What kind of navy do Americans want? The answer will determine whether U.S. power can, in Greenert's formulation, "be where it matters when it matters."

China's naval buildup is eliciting countervailing forces, including Japan's naval expansion, which Greenert says includes ships as capable as ours. Japan's constitution restricts the nation's Self-Defense Forces to just that  defensive activities  but the constitution can be construed permissively to allow, for example, defenses against ballistic missiles and the protection of allies.

This is one reason Greenert says it is reasonable to speak of a 1,000-ship naval force encompassing the assets of nations  such as India, Singapore, Indonesia, Malaysia, Vietnam, New Zealand, Australia, South Korea and the Philippines  that have no agenda beyond maintaining the maritime order on which world commerce depends.

The most momentous naval event in world history, an event more important than the developments of sail and steam power, was the Jan. 17, 1955, signal from the USS Nautilus: "Underway on nuclear power." A nuclear navy can stay on station. Rep. J. Randy Forbes (R-Va.) who chairs the House Armed Services Committee's Subcommittee on Seapower and Projection Forces, notes that with America having fewer land bases overseas, aircraft carriers effectively "move U.S. soil anywhere in the world."

A Chinese intellectual says his country has an "outward-leaning economy." China's economic dynamism, and hence its political stability and geopolitical weight, depends on seaborne imports of natural resources and seaborne exports to distant markets. China, which has territorial disputes in common waters with its neighbors, worries, Forbes says, primarily about America's navy.

Forbes worries about China's development of "carrier-buster" anti-ship missiles that "will back our carriers away from Chinese territory," including those seas that China considers its own. A carrier can cost approximately $13 billion, but that is, Forbes says, acceptable for a product that will project national power for 50 years. The U.S. Navy, with embarked Marines, is the primary instrument for the use of military power.

The question, however, is: Do Americans, demoralized by squandered valor in Iraq and Afghanistan, and dismayed in dramatically different ways by two consecutive commanders in chief  the recklessness of one and the lassitude of his successor  want U.S. power projected? They will answer that question with the Navy their representatives configure. The representatives should act on the assumption that every generation lives either in war years or in what subsequent historians will call "interwar years."